A mattress innerspring comprises a plurality of coil springs including a plurality of perimeter coils defining the perimeter of the innerspring.
A mattress assembly comprises the mattress innerspring sandwiched between a pair of borderwires. The mattress innerspring is secured to the borderwires by means of clips wrapped around a portion of each of the perimeter coils and associated portions of the borderwires.
Apparatuses for securing borderwires on a mattress innerspring are known in the art.
One such apparatus is disclosed in commonly assigned U.S. Pat. No. 4,829,643 entitled "Apparatus and Method For Automatically Securing Borderwires On Mattress Innerspring", to Ayres, et al.
According to Ayres, et al, the mattress assembly is advanced along a horizontal ledge to a clip wrapping station, comprising a pair of spaced clip wrapping tools. As the mattress assembly is advanced along the ledge, sequential alignment of each of the perimeter coils with the clip-wrapping tools is detected by a fiber optic sensor. Upon alignment detection, advancement of the mattress innerspring and borderwires is momentarily stopped, and the clip wrapping tools apply the clips on the borderwires and innerspring, thereby securing them together.
The fiber optic sensing system has proven effective in many applications. However, because the unclipped mattress innerspring and borderwires are not in perfect and consistent alignment, occasional clips were missed, which would have to be manually added later. In addition, the fiber optics had to be readjusted when switching to a mattress innerspring having different size coils. Further, fiber optic devices are inherently susceptible to environmental problems such as dirt accumulation.
Others have utilized computer indexing to determine the position of the innerspring relative to the clip wrapping tool. However, such devices also have problems because of the imperfect alignment of the innerspring coils. In addition, computer indexing adds an undesirable additional level of complexity to the device.
The present invention is provided to solve these and other problems.